Process of treating coal tar impregnated wood with a solution of a compound of boron trifluoride



nite rate i he PROCESS OF TREATING COAL TAR Ill [PREG- NATED WOQD WETH A SGLUTTQN OF A COMPOUND OF BORQN TREFLUOE Karl Friedrich Lang, Frankfurt am Main, Walter Metzendorf, Kronberg (Taunus), Johannes Turowski, Castrop- Rauxel, and Heinrich Gicir, Duishurg-Wanheimerort, Germany, assignors to Rutgerswerlre-Airtiengesellschaft, Frankfurt am Main, Germany No Drawing. Filed July 20, 1959, Ser. No. 828,066 Claims priority, application Germany July 25, 1958 6 Claims. ((31. 11762) This invention relates to the treatment of wood and it has particular relation to the improvement of wood which has been treated with impregnating oils.

It has been known to improve wood, which has been impregnated with impregnating oils, by subjecting the wood to the action of gaseous agents which have a polymen'zing eifect on impregnating oil and as a gaseous agent to be used in this treatment, among others, boron trifiuoride has been suggested. The use of gaseous agents in this process renders it necessary that the treatment of the wood be carried out in a particular chamber and it is difiicult to obtain a predetermined dosage and uniform distribution of the gaseous agent in the wood.

It has now been found that solutions of addition compounds of boron trifluoride with organic acids, such as formic acid, acetic acid, as well as water, alcohols, phenols and ethers, are likewise capable of bringing about a surface resinification of wood impregnated with oil, particularly impregnating oil obtained by distillation of coal tar.

In carrying out the process of this invention, for example BF is introduced into 85 grams of formic acid or acetic acid of 100% until 15 grams of the gaseous BF, are absorbed. If a piece of pine wood (of the dimensions 8 cm. x 4 cm. X 2 cm.) which has been impregnated with impregnating oil from coal tar, is immersed in said solution of BF in acid for 5 minutes and the piece of pine wood thus treated is heated in a drying chamber to 80100 C. for 3060 minutes, the surface of the wood will be completely hardened due to the polymerization of the impregnating oil in the wood. After cooling to ordinary room temperature of e.g. 15-20" C., the pine wood does not give off oil and an oil stain is not formed if the wood is placed on filter paper. The liquid used for hardening the surface of the wood can be applied to the impregnated wood also in other manner, e.g., by spraying.

Solutions of BF are obtained in ethers, alcohols, phenols or water, in a manner analogous to that described above and they can be applied to impregnated wood by immersing the impregnated wood in the solution or spraying the solution to the surface to be treated, by a brush or in other suitable manner.

Hardening of the impregnated wood can be obtained also by treating it with an aqueous solution of HBR;

prepared in conventional manner from B 0 and HF.

Concentration of the BE in the solutions used according to this invention amounts preferably to 15% or more. If complex compounds of BE, with water or alcohol are used, it is of advantage to add to the solution 1l.5% of a conventional inhibitor in order to reduce or prevent corrosion. The inhibitor has no eflfect on polymerization of the impregnating oil. Complexes of BP with others have no corrosive eflect on metallic apparatus or materials. It will be understood that this invention is not limited to the materials, conditions, steps and other details specifically described above and can be carried out with various modifications. Thus, in carrying out the invention any kind of wood, into which impregnating oil has been introduced, can be treated. impregnation with the oil can be carried out in any suitable manner, e.g. by immersion in an open container, or under pressure according to conventional methods. Any kind of oil capable of polymerization and/or resinification can be used, but tar oils, especially coal tar oils, are preferred. The amount of oil in p the wood to be treated corresponds to conventional standards.

Heating of the Wood treated with BF addition compounds promotes and expedites polymerization and hardening.

The parts and percent mentioned above are by weight if not otherwise stated.

What is claimed is:

1. A process for the treatment of wood treated with an oil obtained by distillation of coal tar, comprising contacting said wood with the solution of an addition compound of boron trifiuoride and a substance selected from the group consisting of organic acids, hydrofluoric acid, alcohols, phenols, ethers and water in order to polymerize said tar oil and harden the surface of the wood.

2. A process as claimed in claim 1, in which an addition compound of BF with an organic acid is used.

3. A process as claimed in claim 1, in which an aqueous solution of HBF, is used.

4. A process as claimed in claim 2, in which an addition compound of BF with formic acid is used.

5. A process as claimed in claim 2, in which an -addi tion compound of B1 with acetic acid is used.

6. A process as claimed in claim 1, in which the resulting wood is subjected to heating.

References Cited in the file of this patent UNITED STATES PATENTS 1,463,884 Gardner Aug. 7, 1923 1,739,597 Kessler Dec. 17, 1929 1,886,759 Taylor Nov. 8, 1932 2,066,583 Shipley Jan. 5, 1937 2,425,671 Crandall et al Aug. 12, 1947 2,439,108 Staehle Apr. 6, 1948 2,478,451 Berger et a1 Aug. 9, 1949 2,766,312 Serniuk Oct. 9, 1956 

1. A PROCESS FOR THE TREATMENT OF WOOD TREATED WITH AN OIL OBTAINED BY DISTILLATION OF COAL TAR, COMPRISING CONTACTING SAID WOOD WITH THE SOLUTION OF AN ADDITION COMPOUND OF BORON TRIFLUORIDE AND A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF ORGANIC ACIDS, HYDROFLUORIC ACID, ALCOHOLS, PHENOLS, ETHERS AND WATER IN ORDER TO POLYMERIZE SAID TAR OIL AND HARDEN THE SURFACE OF THE WOOD. 